"Eil, Eil, l'mana sh'wik-thani."
This is really pretty devastating to your entire case. First, this is literally the same thing that is in the Greek NT, only instead of a transliteration from Aramaic into English it's transliterated from Aramaic into Greek. Regardless, the "Aramaic" (Syriac) of the Pe****ta has the same line as the Greek.
Second, what's especially interesting about this is that the Greek version needs more than just a transliteration. Many people read Greek compared to the precious few who read Aramaic. So in the Greek we get the transliteration and the translation: Ἠλὶ ἠλὶ λεμὰ σαβαχθάνι; τοῦτʼ ἔστιν· Θεέ μου θεέ μου, ἱνατί με ἐγκατέλιπες. The first part is Aramaic, which is followed by a translation beginning with "that is, 'My god, my god, why do you forsake me?"
Here's the curious part. If the Pehistta were some original version,
why does it also have both a transliteration and a translation? It makes no sense. Because in the Pe****ta, we find "My god my god, why have you forsaken me, that is, my god, my god, why have you forsaken me?" The transliteration that is in the Greek text is there, along with "that is" (which, in the Greek makes sense as the author uses it to go from the transliteration to the translation). Then the text gives the translation. Only, because both lines are in Syriac, the transliteration
is a translation and the line is simply repeated.
This makes perfect sense when you realize that the Pe****ta isn't original. It's a translation of the Greek. In the Greek, the line isn't repeated because we first have a transliteration, not a translation. In the Pe****ta, the transliteration into Syriac gives us the translation and the line is simply redundant. Yet it's there. Why? Because it isn't original. It's a translation from the Greek, and the translators faithfully stuck the original line in there even though it doesn't make sense in Syriac.